"Chim Chim Cher-ee," written by Richard Sherman and Robert Sherman, performed by Randy Kerber; "One Mint Julep," written by Rudy Toombs, performed by Ray Charles, courtesy of The Ray Charles Foundation, under license from the Ray Charles Marketing Group; "Big Noise From Winnetka," written by Ray Bauduc, Bob Haggart, Bob Crosby and Gil Rodin, performed by The Swing Masters, courtesy of Dare Records; "Lassie Main Title," written by Les Baxter, courtesy of Classic Media, LLC; "Wonderful World of Color," written by Richard Sherman and Robert Sherman, performed by The Wellingtons, courtesy of Walt Disney Records; "Heigh-Ho," written by Frank Churchill and Larry Morey, performed by The Dave Brubeck Quartet, courtesy of Derry Music Company; "Chim Chim Cher-ee," written by Richard Sherman and Robert Sherman, performed by Jason Schwartzman and B.J. Novak; "This Is Not Goodbye," written by Marc Ferrari and Daniel May, performed by Daniel May, courtesy of FirstCom Music; "Supercalifragilisticexpialidocius," written by Richard Sherman and Robert Sherman, performed by Jason Schwartzman and B.J. Novak; "A Kiss Under The Stars," written by Marc Ferrari and Daniel May, performed by Daniel May, courtesy of FirstCom Music; "A Spoonful of Sugar," written by Richard Sherman and Robert Sherman, performed by Jason Schwartzman and B.J. Novak; "Feed The Birds," written by Richard Sherman and Robert Sherman, performed by Jason Schwartzman; "A Man Has Dreams," written by Richard Sherman and Robert Sherman, performed by Jason Schwartzman and Tom Hanks; "Fidelity Fiduciary Bank," written by Richard Sherman and Robert Sherman, performed by Jason Schwartzman, B.J. Novak and Bradley Whitford; "Estudiantina," arranged and performed by Mark Mothersbaugh, courtesy of Mutato Muzika; "Blaydon Races," arranged by Charles Ernest Catcheside-Warrington; "Men of Harlech," arranged by Marshall Bowen; "A Dream Is a Wish Your Heart Makes," written by Al Hoffman, Jerry Livingston and Mack David; "Zip-A-Dee-Doo-Dah," written by Allie Wrubel and Ray Gilbert; "Mary Poppins Medley: A Spoonful of Sugar/Jolly Holiday/Feed The Birds," written by Richard Sherman and Robert Sherman, performed by Arthur Fiedler and The Boston Pops Orchestra, courtesy of The Decca Music Group, under license from Universal Music Enterprises; "A Spoonful Of Sugar," written by Richard Sherman and Robert Sherman, performed by Julie Andrews, courtesy of Walt Disney Records; "Jolly Holiday," written by Richard Sherman and Robert Sherman, performed by Dick Van Dyke and Julie Andrews, courtesy of Walt Disney Records; "Step In Time," written by Richard Sherman and Robert Sherman, performed by Dick Van Dyke, courtesy of Walt Disney Records; "Let's Go Fly A Kite," written by Richard Sherman and Robert Sherman, performed by David Tomlinson, Dick Van Dyke and The Londoners, courtesy of Walt Disney Records; "Mary Poppins Overture," written by Richard Sherman and Robert Sherman, performed by "Orchestra," courtesy of Walt Disney Records.

On 2 April 1961 in London, England, children's author P. L. Travers is roused from a memory of her beloved, eccentric father by the arrival of her literary agent, Diarmuid Russell. He has come to escort her to the airport, as she is travelling to Los Angeles, California, to meet producer Walt Disney. The filmmaker has been trying to option the film rights to Travers' Mary Poppins series for twenty years, but she suddenly declares the deal is off. Although Travers despises the Disney brand of happy endings, Russell warns his client that her books are no longer generating royalties, and she will soon lose her house. When he reminds her of Disney's promise to refrain from making an animated film, Travers grudgingly agrees to resume her two-week business trip on condition that she will not sign the contract until she is satisfied with the script. As Travers boards the airplane, she remembers herself as a child, leaving her comfortable home in Maryborough, Australia, for the remote Queensland outpost of Allora, where her father accepted a new job as bank manager. Upon arrival in Los Angeles, Travers is chauffeured to the Beverly Hills Hotel by a cheery man named Ralph, and is horrified to find her room overflowing with Disney merchandise. Later, at the Walt Disney Studios in Burbank, Travers meets Don DaGradi, who has been hired to adapt her work, as well as songwriting brothers Richard and Robert Sherman, but she bitterly declares her opposition to making a musical. She insists on meeting Disney, and is disconcerted by his informality, but learns that he was introduced to Mary Poppins by his own daughters. Having promised the girls that he would make a film version of their favorite book, Disney will stop at nothing to produce Mary Poppins and declares that it will be a "revolutionary" picture. Taking Travers' hands in his, Disney vows to uphold the book's integrity. However, Travers regards her characters as "family" and refuses to sign a contract. Insisting that all conversations be tape-recorded to verify verbal agreements, Travers reconvenes with DaGradi and the Sherman brothers to review the screenplay. However, she is unfamiliar with staging and scene descriptions, and is displeased by the song, "Chim Chim Cher-ee." She later disparages production designs, and insists that the Banks family should not be portrayed as wealthy. When Disney learns of Travers' incessant nitpicking, he attempts to appease her, but the author is still intent on withholding screen rights. Back at the Beverly Hills Hotel bar, Travers orders tea and again remembers her father, whose alcoholism threatened the family's security. Back at Disney Studios, the Sherman brothers compose "A Spoonful Of Sugar," but Travers finds the lyrics patronizing. She declares that Mary Poppins, unlike Disney, is "the enemy of whimsy and sentiment." She orders the men to find the "gravitas" of the narrative, then throws the script out the window. In her hotel room that evening, Travers telephones her agent to complain that she is "at war with herself." Remembering her father's refrain, "Life is an illusion," Travers believes that her childhood imagination created conflict between her parents, and provoked her father's alcoholism. Sometime later at the studio, the Sherman brothers perform their song, "Fidelity Fiduciary Bank." As she listens, Travers is haunted by a memory of her father, who embarrassed his family and bank executives by getting drunk before an Allora county fair awards ceremony. When the Shermans' lyrics mock the character "Mr. Banks," whom Travers modeled after her father, the author protests, declaring, "He was not a monster!" Suppressing tears, Travers walks away from the baffled men, muttering regret that she let her father down yet again and remembering how he suffered withdrawal from alcohol. The man's condition became so hopeless, Travers' mother attempted suicide, but tranquility was temporarily restored by the arrival of the magical yet practical Aunt Ellie, who became a model for "Mary Poppins." After her father finally succumbed to his illness and died, Travers blamed her Aunt Ellie for failing to remedy the family tragedy. Back in the present, Ralph notices Travers on the Disney Studio lot lawn, diverting her attention to fallen leaves. He comforts the writer, reflecting that his daughter is bound to a wheelchair and he fears for her future, but he has learned to "live for today." Travers, who notes that she has no family, creates a miniature bandstand with the leaves, portraying a scene from Mary Poppins, and Ralph wishes aloud that he could show his daughter the mystical places within Travers' imagination. Later, at the Beverly Hills Hotel, Travers receives a telephone call from Disney, who wonders aloud how to make his "favorite author" happy. He insists that she accompany him to Disneyland, "the happiest place on Earth," and despite Travers' protests, Ralph chauffeurs her to the theme park the following day. There, Disney forces her to ride the merry-go-round and announces that his writing team has come up with a new approach to "Mr. Banks." The next day at the studio, Travers is finally won over by a rendition of the song "Let's Go Fly A Kite," which portrays Mr. Banks mending his children's kite and gives the film an uplifting conclusion. However, Travers is outraged to learn that the picture will include animation. Feeling betrayed by Disney, she returns her contract unsigned, and goes back to London. Meanwhile, Disney learns that Travers' identity is fictitious; her birth name is "Helen Goff," and she is Australian by birth rather than a high-class Englishwoman. He takes the next flight to London and shows up at Travers' doorstep, announcing that she has misjudged him. Disney suggests that disappointments in life have led Travers to hold faith only in Mary Poppins, but Travers counters that the character is merely fiction. In response, Disney reveals his knowledge that Travers created a fictional personality for herself, to conceal childhood wounds. Disney admits he was abused by his own father, but declares that he is tired of feeling sad about the past. He implores Travers to share her story with the world and allow him to transform it into a tale of hope and joy. Disney divulges his knowledge that the author adopted her father's first name, "Travers," as her own pseudonym surname, and encourages the woman to forgive her former self, the young "Helen Goff." He wants to paint a fresh picture of the troubled, yet endearing elder Travers Goff, and redeem the man in Mary Poppins. Sometime later, Travers finally signs the contract, and the film is produced. Although Disney does not invite Travers to the premiere, she shows up anyway. Ralph chauffeurs her to the Chinese Theatre, insisting that the film would have been impossible without her brilliant imagination. Watching Mary Poppins on the big screen, Travers cries aloud, remembering her father's promise to never leave her.